Sulfurized nitriles and process of preparing the same



Dec. 6, 1949 s. E. JOLLY 2,490,271

' SULFURIZED NITRILES -AND PROCESS OF PREPARING THE SAME Filed June 25, 1945 Patented Dec. 6, 1949 SULFURIZED NITRILES AND PROCESS. OF 1 PREPARING THE SAME Samuel -Edward Jolly, Prospect Park, Pa., a'ssignor -toSun-0il(3ompany, Philadelpha,'la., a corporation-of. New .-J ersey Application June 25, 1943, Serial' N0.\.492,227

Y 3 Claims.

v l This 'invention wrelates to suluriZed lnitriles and to their preparation, and more particularly concerns sulfurized `nitrileswhich .are soluble inmineral lubricating Oilsand'which have characteristics imparting utility as special lubricants.l The invention .particularly ,contemplates .;,t-he preparation of oil.-.soluble sulfurized :.Jnitriles from .molecular. weight organic acids, suchy asfatty and rosin acids, in two; major :steps comprising starting materials containing `higher conversion of the acids to .nitriles .andsulfurizaytion 1 of the nitriles.

. NumerOusLmethOds of A.convertingfatty .acids into. nitriles.. .are.zknown,.. some :of which.. are .of .only academicinterest while othershave. shown commercial value. In.Z the .latterV methods .the conversion Ygenerally 'has been effected by causing .the fatty .'.acids andoammonia to react .in Seither .liquid or 'vapori phase according to .the f following :reactions armethod of effecting these reactionsin liquid phase,and Potts et a1..U. S. Patent A2,314,894 discloses :1 an. improved Amethodfcomprising bOth liquid Aand vapor.l phase .reactions. Methods whereingthese reactions` have been Vcarried out -wholly infvaporphase in many cases have proved unsatisfactory due to ,decompositionrof `the fatty acids on vaporization.: In the present .invention the. methods disclosed in 'ther abovementioned patents as .well/as other known methods may be used to form thei nitriles fromxsome starting Amaterials; however',l with certain preferred starting material, these methods are not altogether satisfactory-.as iswmore fully explained hereinafter.l .Accordingly .an improvedmethod, which more adequately fulfills requirementsof the present invention, hasbeen devised and the inventionincludes-.as one of' its vfeatures such f improved method for.` convertingv organic acids to nitriles.

' It is known to preparefcertain reaction products from fatty .acid nitriles for .use in extreme distinction the;sulfurizedproducts of the present invention, which are preparedby reacting free sulfur. with ynitriles under: specially controlled conditions -and'whichalsofare'- valuable in the f--ma'nufacture of'` lubricantsito Vbe usedl'under Ralston et. al., lU., S.v Patent 2,061,314f discloses severe. service conditions, contain chemically vcombined sulfursbut no chlorine.

In accordance. with Athis invention, oil-soluble sulfurized .nitrilesare prepared from starting materials .such .as stearic acid, oleic acid, lard oil acids and .other fatty acids vof animal, vegetable or marineorigin which have at least Vten .carbon atoms, but particularly from talloil .which is a mixture .of fatty andfrosin acids obtained as al by-product; in paper manufacture from pine :andother non-deciduous woods, first by forming nitrilesunder conditionssuch that no substantialamount of-reactionproducts boilingabove the boilingrange of .the starting acids are formed, and then reacting the so-formed nitriles with freesulfurat an elevated temperature for a length oftime sufficient to give a homogeneous productbut,insufcient to cause the formationr ofmineral-oil-insoluble products. I have discovered.thatnitrileswhich are higher boiling than the..starting acids from which they v were prepared, apparently due .to polymerization duringtheinformation, on sulfurizing yield vproducts =which.vare substantially .oil-insoluble and therefore unsuitable in the-present application. Further; I-have discovered that nitriles,

even though ethey-may-be of .suitable boiling range, 'likewise yield substantially oil-insoluble .products on 1sulfurization unlessthe reaction between-the nitriles-.and sulfur; is-carried out. in relatively-short time.

"When such starting materials .-as stearicacid,

- oleic acid orglard oilacds are used, various heretofore `known .methods of preparing;- the nitriles 35:

.talloil dueto vits-;availability and low cost, and

are suitable. .However, it is preferred to use with this starting material these known methods generallyygive a product containing a consider- I able proportion of nitriles which boil higher than the boiling range. ofthe talloil and'which on sulfurization form undesirable oil-insoluble products. .Inorder-to-usenitriles prepared from tall- 1 oil according to methods `heretofore known, it v`usually is necessary to. remove the high boiling -materiahfor instance by distillation, thus sacri- Aiicing` yield vof nitriles `in order to obtain the desired .-quality. I: have-l discovered that nitriles `of suitablef'boiling-rangemay be prepared from talloilH4 in accordance with; the reactions vlisted above by contacting-the talloil in liquid phase and lat elevated '..temperature with ammonia fvapor. vunder suchftconditions that the time of contact is relativelyffshort, for instance not more thanv say twenty minutes; and preferably less if possible. Thiscausesthe desired reactions to proceed .without allowing the reactions that result in the formationrof high boiling nitriles to take place to a substantial extent. In order to obtain the desired-high yield in such shortvtime 60 of contactitobviously` is requisite that very intimate contact between the talloil and ammonia vapor be effected, and it has been found that a packed column provides a particularly suitable means of effecting an intimate but short-timed contact. Further, it is desirable to carry out the reaction in the presence of a dehydrating catalyst such as alumina or silica gel in order to accelerate the reaction, and a preferable means of accomplishing this is by employing catalyst as the packing material for the contact column. Thus the preferred method of preparing nitriles according to the invention comprises continuously feeding heated talloil to the top of a contact column packed with a dehydrating catalyst, continuously passing ammonia vapor through the column and allowing the talloil to trickle over the catalyst and flow by gravity to the base of the column, thereby effecting an intimate contact of short duration be tween the liquid and vapor phases.

The optimum temperature range for carrying out the contact operation between talloil and ammonia vapor has been found to be about B-375 C., this giving the maximum yield of nitriles of suitable boiling range. Temperatures below 325 C. tend to cause decreased rate of reaction, thus requiring a longer time of contact with a resultant increase in the proportion of undesirable high-boiling material formed. Temperatures above 375 C. tend to cause decreased yield of desirable nitriles, possibly by causing cracking of the reaction products, cracking of the talloil itself and perhaps an unfavorable displacement in the equilibrium of the first step of reaction illustrated by Equation l, supra.

Sulfurization of the nitriles is accomplished by reacting elemental sulfur with the nitriles and may be carried out in either batch or continuous manner. There are two critical, interrelated factors involved in this step, namely, the reaction temperature and the time of reaction. In order to initiate the reaction between nitriles and sulfur, a temperature of about 190 C. is required. A temperature such as 180 C., although not considerably below 190 C., gives an exceedingly slow rate of reaction. After the reaction has been initiated by raising the temperature of a mixture of nitriles and sulfur to 190 C., there is a tendency toward further increase in temperature due to the exothermic nature of the reaction. This is not objectionable provided the processing equipment is properly designed for handling the materials at higher temperature with safety. A short reaction time is exceedingly important in preventing formation of undesirable oil-insoluble reaction products of a sludge-like nature. Thus it is desirable that the reaction be allowed to proceed only so long as to give a product which will be homogeneous at ordinary temperature but not so long as to cause formation of such oil-insoluble products. The proper time of reaction depends on the proportion of sulfur used and the reaction temperature; the less the proportion of sulfur and the higher the reaction temperature, the shorter being the required reaction time. At a temperature of about i90-200 C., it is desirable that the reaction time be not over about 15 minutes, although somewhat longer reaction times may not be too unsatisfactory for practical operation.

In the accompanying single sheet of drawing there is shown schematically a preferred form of apparatus for practicing the invention, which, for purposes of illustration, is described in connection with the processing of talloil, but which GII is also suitable for the processing of other charge stocks such as stearic acid, oleic acid and lard oil acids.

As shown in the drawing, talloil, which may be either crude or refined and which usually will conform to the following specifications:

Saponication No 170-185 Acid No 160-180 Iodine No -130 Fatty Acids per cent 44-60 Rosin acids, calculated as abietic acid do 34-47 Sterols, higher alcohols,

hydrocarbons, etc d0 6-10 Moisture do 0.1-0.3 Ash -do 0.1

is charged to the process by means of charge pump 2. The tall-oil passes through preheater 3, where its temperature is raised to 325-3'75 C., and into contact column 4. It has been found that talloil at such elevated temperature has a tendency to decompose when not in the presence of ammonia, and in order to prevent such decomposition it is desirable that the time interval between entrance of the oil to preheater 3 and its entrance into contact column 4 be short. It also is desirable to add a small proportion of ammonia to the talloil before preheating as further insurance against decomposition, and line 5 containing valve 6 is provided for this purpose. Contact column 4 is packed with a granular dehydrating catalyst 'I such as alumina, the catalyst being supported at a point above the bottom of the column by a suitable catalyst support 8 such as a wire grille. The entering talloil preferably is distributed evenly on the alumina near the top of contact column 4 by means of a distributor 9 which may be of any suitable form. Ammonia vapor, preferably anhydrous, is preheated to a temperature of S25-375 C. in preheater I0 and is passed into the column suitably at a point just below catalyst support 8. The talloil flows down the column as a thin film on the surfaces of the catalyst and countercurrently to the ascending ammonia vapor stream, thereby intimately commingling with the ammonia. At the top of contact column 4 there is provided vapor outlet line II through which eluent vapors, comprising excess ammonia, water formed in the reaction and any low boiling organic materials present or formed during the reaction, are withdrawn. These vapors preferably are passed through apparatus for separately recovering ammonia and any low boiling organic materials, which is not shown in the drawing since apparatus suitable for accomplishing this is well known and forms no part of the present invention. The liquid stream flows by gravity from the catalyst zone and co1- lects in the base of the column, and sight gauge I2 is provided as an aid in maintaining a low liquid level therein. The liquid level is regulated by means of valve I3 in outlet line I4 or by varying the speed of pump I5. The reaction product which is withdrawn from the base of the column by means of pump I5 consists predominately of nitriles having a boiling range not higher than that of the talloil charge stock, provided the contact column is of suitable height and proper operating conditions are maintained.

Contact column 4 obviously should be insulated or provided with suitable heating means for maintaining a temperature of S25-375 C.

On continued operation the catalyst 'I in contact column 4 usually will decrease inactivity due assiomi tddepositionof small amounts 'of gums, resins or polymerized materials. Regeneration ofthe catalyst may be accomplished, when desired, by Washing with a suitable solvent, for instance, benzene.

The nitrile product withdrawn' fromv the contact column 4 flows through cooler I6, where'its temperature is reduced' preferably to a level such that the temperature within sulfurizing column l1 will be about 190-20090., whence .it passes to the base .of sulfurizing column l1. Sulfur also Ais added near the base of the column in proportion desired for reaction with the nitriles. As illustrated in thedravving,I this may Abedone by feeding nely divided sulfur from hopper I8 to the column by means of screw conveyor I9. Sulfurizing column Il is provided with a stirrer driven by electric motor 2i) and comprising a centrally located shaft along which is attached in suitable space arrangement a plurality of blades or other means for dispersing the sulfur and electing intimate contact between the nitriles and sulfur as the mixture flows up the column. It is desirable that sulfurizing column I'l be of sufficiently small diameter so that the mixing'effected by the stirrer is mainly lateral without a substantial amount of vertical mixing in order that a reasonably deiinite continuous now of the mixture up the column obtains. Sulfurizing column I1 also is provided with 'a plurality of outlet lines 2 la, b, c, d, e, f vertically spaced along its upper section, all provided with valves by means of which the level of withdrawal of reaction products is controlled. With this arrangement the time of reaction between the nitriles and sulfur depends on the rate of ow, the diameter of the sulfurizing column and the level from which the reaction mixture is withdrawn; thus for a given rate of charge to the process the reaction time may be varied as desired by varying the level of withdrawal. In order to maintain the desired short reaction time for various rates of flow, one of the lower levels, for instance line 2Ia, would be used for a slow rate of flow while a higher level, for instance line 2 le, would be used for a faster rate. Obviously the equipment must be properly designed to allow suitable adjustment for any charge rate that may be employed.

The sulfurized nitriles from column I1 flow through cooler 22 and thence may be sent to storage or directly to a blending tank as base stock for compounding special lubricants.

In the step of preparing nitriles from talloil, the importance of a short time of contact as effected in the process described above is illustrated by the following comparison between the present method and a known method comprising prolonged batch treatment of liquid talloil with ammonia vapor:

As indicated by the acid numbers of the products, approximately the same proportion of the charge was converted to nitriles in each case. However, with the known method only 55 per cent of the product waspoftsuitable boilingrange (ire:

not higher than the boiling rangelof the talloil); Whereas 92 per cent `of. the yproduct prepared according to the Vpresent method Was ofv suitable boiling range. Thus the latter product contained only 8 per cent. of .nitrilesrof higher boiling range -an amount insufficient to cause the product onsulfurization `to :yield .oil-insoluble materialwhile the product ofthe known method contained 45 per centr of such higher boiling :nitriles which rendered it unsuitable for, preparation of oilsoluble sulfurized products.

In the step of sulfurizing the nitriles, the im-i portancevof a short reaction time maybe demonstrated by sulfurizing samples of the nitriles for various lengths'oftim'e,mixing the sulfurized samples with mineraloil and notingthe amounts ofA insoluble material, filtering the blends to remove the insoluble` material, then allowingthe filtered blends to age at alow temperature yand noting any `further formation of insoluble material. The data given below are illustrative of experiments of this type which have been made with nitriles prepared from talloil according to the method described above. In each of these experiments 25 parts of sulfur Were reacted with parts of nitriles at a -temperaturefof 190-200 C., and 10 parts of the resulting sulfurized nitriles were blended with parts of mineral oil.

Amount of insoluble material in unllltered blend Reaction time, minutes Observations on filtered blend after aging at 6 C.

trace no separation after 30 days of aging. precipitate after 6 days of aging; black sludge after 8 days of aging.

precipitate after 3 day of aging; black sludge after 7 days of aging.

small amount considerable amount This tabulation indicates that a reaction time less than 35 minutes is required in order to produce stable products.

sulfurized nitriles prepared as described herein are useful base stock for manufacture of special lubricants for use in severe service, such as nonemulsiable mild extreme pressure lubricants, emulsiable cutting oil, and greases. A preferable sulfur content for such base stock is 20-25 per cent, although it is not diicult to incorporate somewhat higher proportions of sulfur in the nitriles. In preparing moderately extreme pressure lubricants, this base stock may be blended with any type of mineral oil of suitable viscosity and ash point, 10 parts of base stock to 90 parts of oil being a usual proportion although more or less may be desirable depending on the particular use to which the product is to be put.

The sulfurized nitriles may be made suitable for use in the preparation of special lubricants which are non-corrosive to such metals as brass, copper, bronze and aluminum, by treatment with an alkali to remove free or loosely bound sulfur.

sulfurized esters or glycerides of fatty acids have been used in various special lubricants. In many cases sulfurized nitriles may be used to advantage in place of the sulfurized esters or glycerides. For instance, lubricants which contain esters or glycerides may undergo hydrolysis or become rancid, thus developing an acidity which renders these materials corrosive. Furthermore this hydrolysis also may be objectionable since many of these lubricants, for best performance, should be slightly alkaline, as is the case with variousfslubl oils and greases. Sulfurized ni triles, on the other hand, do not undergo hydrolysis under conditions encountered in service and therefore have particular utility in the manufacture of such special lubricants.

Many modifications in apparatus and method of operation for practicing the invention will be apparent, and it is to be understood that the invention is not to be limited to the particular embodiment disclosed and described herein.

I do not herein claim the hereindescribed lubricant, the same formingthe subject matter of a divisional application led October 28, 1943, Serial No. 508,061, now U. S. Patent 2,380,531.

I claim:

1. As a new composition of matter, oil-soluble sulfurized nitriles of organic acids having at least containing essentially only the elements derived 2;,

from the nitriles and the sulfur.

3. The method of sulfurizing nitriles of talloil in order to produce a substantially oil-soluble sulfurized product which comprises reacting said nitriles with sulfur at a temperature not substane tially less than 190 C. but below the decompos; tion temperature of the sulfurized nitriles for a time of at least five minutes but less than thirtyve minutes. n

SAMUEL EDWARD J OLIXl REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,116,472 Ralston May 3, 1938 2,125,853 Ralston Aug. 2, 1938 2,141,142 Ralston Dec. 20, 1938 2,218,918 Loane Oct. 22, 1940 2,230,390 Signaigo Feb. 4, 1941 FOREIGN PATENTS Number Country Date 390,120 Great Britain Mar. 30, 1933 

